docs: def build_weights(realizations, imt_dt):
      """
      :returns: an array with the realization weights of shape (R, M)
      """
      arr = numpy.zeros((len(realizations), len(imt_dt.names)))
      for m, imt in enumerate(imt_dt.names):
          arr[:, m] = [rlz.weight[imt] for rlz in realizations]
      return arr